1. Field of the Invention
This invention relates to reverse pressure face seals for use in jet engines and other turbomachinery to reduce or even to prevent oil weepage through an interface between a seal member and a mating ring when there is a pressure reversal in the sealed chamber or tunnel portion of the engine.
2. Description of the Prior Art
Face seal assemblies for jet engines and other turbomachinery are known and typically include a rotating ring together with a stationary sealing member biased against the ring to prevent leakage therebetween. Lubricating oil typically flows outwardly through generally radial holes in the mating ring, exiting on the outer diameter of the ring. The oil on the outer diameter of the ring, typically referred to as the “oil side”, is blocked against flow back into the space within the ring, typically referred to as the “air side”, by the sealing member that is biased against the ring. When there is a pressure reversal in the interior chamber, or tunnel, which is the “air side” of the engine, pressure in the “air side” area of the engine drops to a level below the pressure on the “oil side”, which may be located close to the exterior of the engine. The pressure reversal causes air to flow radially inwardly into the interior chamber or tunnel on the “air side” of the face seal in the engine, causing small amounts of oil to leak past the face seal. This radially inwardly leaking oil passing the seal, called “oil weepage” in the trade, is deleterious to the engine and, in aircraft engines, may result in the odor of oil leaking into the passenger cabin. Such pressure reversal may occur when the “reverse thrust” capability of the engine is used.